No Cell Phones Please Thank You Specialty Foundation

No Cell Phones, Please. Thank You.

Specialty Foundation Construction Jet Grouting Drilled Micropiles Vibratory Ground Improvement & Stone Columns Construction Drilling, Grouting & Anchors Central Artery / Tunnel Project Contract C 09 C 1 US Interstate 90 & Interstate 93 Interchange Boston, Massachusetts Presented By: Pier Luigi Iovino, Division President Division of Layne Christensen Company

Design Applications APPLICATIONS… u u Temporary Condition u Underpinning support of an abutment u 22 drilled micropiles installed Permanent Foundation Support u Support for new bridge foundation u 90 drilled micropiles installed

Design Applications INSTALLATION TECHNIQUES… u u Drilled micropiles were steel reinforced and cement grouted with a minimum rock socket diameter of 8 -inches. Rotary drilling technique utilized, with a permanent 5. 5 -inch O. D. steel casing connected to a 7 -7/8 -inch O. D. drill bit.

Design Applications SIGNIFICANCE… u u Central Artery/Tunnel (CA/T) project is funded through the US Federal Highway Administration (FHWA). Drilled micropiles are newly accepted method in US. Drilled micropiles used as permanent bridge foundation component for FHWA funded project. de facto acceptance of drilled micropiles as viable solution.

Design Considerations THREE COMPONENTS… u Threaded casing test results u tension; compression and bending u Structural / Seismic u Geotechnical

Temporary Condition

Temporary Condition STRUCTURAL CONSIDERATIONS… u Pile Capacity = 67 tons / 134 kips. u Pile Diameter = 8 inches u Allowable design compressive stress of grout = 4, 000 x 0. 33 psi.

Temporary Condition GEOTECHNICAL CONSIDERATIONS… u Bearing stratum in bedrock. u Allowable friction stress in bedrock = 45 psi. u Length of rock socket = u u u 134 x 1000/(8 x 3. 14 x 45 x 12) = 9. 87 feet Pile lengths to be 100 to 135 feet with 10 feet into bedrock.

Installation of Drilled Micropiles for Temporary Underpinning of Abutment Drilled piles were installed in low headroom as part of a value engineered proposal replacing contract design of driven piles.

Permanent Foundation Support

Permanent Foundation Support STRUCTURAL CONSIDERATIONS… u Pile Capacity = 100 tons / 80 kips. u Pile Lateral Capacity = 2 kips. u Pile Diameter = 9 inches. u u Steel pipe to be 7 inches diameter, O. D. t=0. 5” N-80 steel. Allowable design compressive stress of grout = 4, 000 x 0. 33 psi.

Permanent Foundation Support GEOTECHNICAL CONSIDERATIONS… u Bearing stratum in bedrock. u Pile to be minimum 12 feet into bedrock. u Skin friction area = u u 9 x 3. 14 x 12 u = 4069. 4 sq. in. Rock/grout friction stress = u 200 x 1000/4069. 4 u = 49. 1 psi

Pile Load Test Frame

Pile Load Test Frame

Installation of Drilled Micropiles for Permanent Bridge Foundation Support

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